2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
33 #include "ucioption.h"
37 //// Local definitions
42 const int Sign[2] = { 1, -1 };
44 // Evaluation grain size, must be a power of 2
45 const int GrainSize = 8;
47 // Evaluation weights, initialized from UCI options
48 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
52 #define S(mg, eg) make_score(mg, eg)
54 // Internal evaluation weights. These are applied on top of the evaluation
55 // weights read from UCI parameters. The purpose is to be able to change
56 // the evaluation weights while keeping the default values of the UCI
57 // parameters at 100, which looks prettier.
59 // Values modified by Joona Kiiski
60 const Score WeightsInternal[] = {
61 S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
64 // MobilityBonus[PieceType][attacked] contains mobility bonuses for middle and
65 // end game, indexed by piece type and number of attacked squares not occupied
66 // by friendly pieces.
67 const Score MobilityBonus[][32] = {
69 { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
70 S( 31, 22), S( 38, 27), S( 38, 27) },
71 { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
72 S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
73 S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
74 { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
75 S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
76 S( 29,116), S( 30,117), S( 31,118), S(32,118) },
77 { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
78 S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
79 S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
80 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
81 S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
82 S( 20, 35), S( 20, 35) }
85 // OutpostBonus[PieceType][Square] contains outpost bonuses of knights and
86 // bishops, indexed by piece type and square (from white's point of view).
87 const Value OutpostBonus[][64] = {
90 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
91 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
92 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
93 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
94 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
95 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0),
96 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
97 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) },
99 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
100 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
101 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
102 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
103 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
104 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0),
105 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
106 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) }
109 // ThreatBonus[attacking][attacked] contains threat bonuses according to
110 // which piece type attacks which one.
111 const Score ThreatBonus[][8] = {
113 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
114 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
115 { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
116 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
119 // ThreatedByPawnPenalty[PieceType] contains a penalty according to which
120 // piece type is attacked by an enemy pawn.
121 const Score ThreatedByPawnPenalty[] = {
122 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
127 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
128 const Score RookOn7thBonus = make_score(47, 98);
129 const Score QueenOn7thBonus = make_score(27, 54);
131 // Rooks on open files (modified by Joona Kiiski)
132 const Score RookOpenFileBonus = make_score(43, 43);
133 const Score RookHalfOpenFileBonus = make_score(19, 19);
135 // Penalty for rooks trapped inside a friendly king which has lost the
137 const Value TrappedRookPenalty = Value(180);
139 // The SpaceMask[Color] contains the area of the board which is considered
140 // by the space evaluation. In the middle game, each side is given a bonus
141 // based on how many squares inside this area are safe and available for
142 // friendly minor pieces.
143 const Bitboard SpaceMask[2] = {
144 (1ULL << SQ_C2) | (1ULL << SQ_D2) | (1ULL << SQ_E2) | (1ULL << SQ_F2) |
145 (1ULL << SQ_C3) | (1ULL << SQ_D3) | (1ULL << SQ_E3) | (1ULL << SQ_F3) |
146 (1ULL << SQ_C4) | (1ULL << SQ_D4) | (1ULL << SQ_E4) | (1ULL << SQ_F4),
147 (1ULL << SQ_C7) | (1ULL << SQ_D7) | (1ULL << SQ_E7) | (1ULL << SQ_F7) |
148 (1ULL << SQ_C6) | (1ULL << SQ_D6) | (1ULL << SQ_E6) | (1ULL << SQ_F6) |
149 (1ULL << SQ_C5) | (1ULL << SQ_D5) | (1ULL << SQ_E5) | (1ULL << SQ_F5)
152 // King danger constants and variables. The king danger scores are taken
153 // from the KingDangerTable[]. Various little "meta-bonuses" measuring
154 // the strength of the enemy attack are added up into an integer, which
155 // is used as an index to KingDangerTable[].
157 // KingAttackWeights[PieceType] contains king attack weights by piece type
158 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
160 // Bonuses for enemy's safe checks
161 const int QueenContactCheckBonus = 3;
162 const int QueenCheckBonus = 2;
163 const int RookCheckBonus = 1;
164 const int BishopCheckBonus = 1;
165 const int KnightCheckBonus = 1;
167 // InitKingDanger[Square] contains penalties based on the position of the
168 // defending king, indexed by king's square (from white's point of view).
169 const int InitKingDanger[] = {
170 2, 0, 2, 5, 5, 2, 0, 2,
171 2, 2, 4, 8, 8, 4, 2, 2,
172 7, 10, 12, 12, 12, 12, 10, 7,
173 15, 15, 15, 15, 15, 15, 15, 15,
174 15, 15, 15, 15, 15, 15, 15, 15,
175 15, 15, 15, 15, 15, 15, 15, 15,
176 15, 15, 15, 15, 15, 15, 15, 15,
177 15, 15, 15, 15, 15, 15, 15, 15
180 // KingDangerTable[Color][attackUnits] contains the actual king danger
181 // weighted scores, indexed by color and by a calculated integer number.
182 Score KingDangerTable[2][128];
184 // Pawn and material hash tables, indexed by the current thread id.
185 // Note that they will be initialized at 0 being global variables.
186 MaterialInfoTable* MaterialTable[MAX_THREADS];
187 PawnInfoTable* PawnTable[MAX_THREADS];
189 // Function prototypes
190 template<bool HasPopCnt>
191 Value do_evaluate(const Position& pos, EvalInfo& ei);
193 template<Color Us, bool HasPopCnt>
194 void init_attack_tables(const Position& pos, EvalInfo& ei);
196 template<Color Us, bool HasPopCnt>
197 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
199 template<Color Us, bool HasPopCnt>
200 void evaluate_king(const Position& pos, EvalInfo& ei);
203 void evaluate_threats(const Position& pos, EvalInfo& ei);
205 template<Color Us, bool HasPopCnt>
206 int evaluate_space(const Position& pos, EvalInfo& ei);
209 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
211 inline Score apply_weight(Score v, Score weight);
212 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
213 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
223 /// Prefetches in pawn hash tables
225 void prefetchPawn(Key key, int threadID) {
227 PawnTable[threadID]->prefetch(key);
230 /// evaluate() is the main evaluation function. It always computes two
231 /// values, an endgame score and a middle game score, and interpolates
232 /// between them based on the remaining material.
233 Value evaluate(const Position& pos, EvalInfo& ei) {
235 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei)
236 : do_evaluate<false>(pos, ei);
241 template<bool HasPopCnt>
242 Value do_evaluate(const Position& pos, EvalInfo& ei) {
244 ScaleFactor factor[2];
247 assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
248 assert(!pos.is_check());
250 memset(&ei, 0, sizeof(EvalInfo));
252 // Initialize by reading the incrementally updated scores included in the
253 // position object (material + piece square tables)
254 ei.value = pos.value();
256 // Probe the material hash table
257 ei.mi = MaterialTable[pos.thread()]->get_material_info(pos);
258 ei.value += ei.mi->material_value();
260 // If we have a specialized evaluation function for the current material
261 // configuration, call it and return
262 if (ei.mi->specialized_eval_exists())
263 return ei.mi->evaluate(pos);
265 // After get_material_info() call that modifies them
266 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
267 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
269 // Probe the pawn hash table
270 ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
271 ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
273 // Initialize attack bitboards with pawns evaluation
274 init_attack_tables<WHITE, HasPopCnt>(pos, ei);
275 init_attack_tables<BLACK, HasPopCnt>(pos, ei);
278 evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
279 evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
281 // Kings. Kings are evaluated after all other pieces for both sides,
282 // because we need complete attack information for all pieces when computing
283 // the king safety evaluation.
284 evaluate_king<WHITE, HasPopCnt>(pos, ei);
285 evaluate_king<BLACK, HasPopCnt>(pos, ei);
287 // Evaluate tactical threats, we need full attack info including king
288 evaluate_threats<WHITE>(pos, ei);
289 evaluate_threats<BLACK>(pos, ei);
291 // Evaluate passed pawns, we need full attack info including king
292 evaluate_passed_pawns<WHITE>(pos, ei);
293 evaluate_passed_pawns<BLACK>(pos, ei);
295 Phase phase = ei.mi->game_phase();
297 // Middle-game specific evaluation terms
298 if (phase > PHASE_ENDGAME)
300 // Evaluate pawn storms in positions with opposite castling
301 if ( square_file(pos.king_square(WHITE)) >= FILE_E
302 && square_file(pos.king_square(BLACK)) <= FILE_D)
304 ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
306 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
307 && square_file(pos.king_square(BLACK)) >= FILE_E)
309 ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
311 // Evaluate space for both sides
312 if (ei.mi->space_weight() > 0)
314 int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
315 ei.value += apply_weight(make_score(s * ei.mi->space_weight(), 0), Weights[Space]);
320 ei.value += apply_weight(ei.mobility, Weights[Mobility]);
322 // If we don't already have an unusual scale factor, check for opposite
323 // colored bishop endgames, and use a lower scale for those
324 if ( phase < PHASE_MIDGAME
325 && pos.opposite_colored_bishops()
326 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > VALUE_ZERO)
327 || (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < VALUE_ZERO)))
331 // Only the two bishops ?
332 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
333 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
335 // Check for KBP vs KB with only a single pawn that is almost
336 // certainly a draw or at least two pawns.
337 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
338 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
341 // Endgame with opposite-colored bishops, but also other pieces. Still
342 // a bit drawish, but not as drawish as with only the two bishops.
343 sf = ScaleFactor(50);
345 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
347 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
351 // Interpolate between the middle game and the endgame score
352 return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
357 /// init_eval() initializes various tables used by the evaluation function
359 void init_eval(int threads) {
361 assert(threads <= MAX_THREADS);
363 for (int i = 0; i < MAX_THREADS; i++)
368 delete MaterialTable[i];
370 MaterialTable[i] = NULL;
374 PawnTable[i] = new PawnInfoTable();
375 if (!MaterialTable[i])
376 MaterialTable[i] = new MaterialInfoTable();
381 /// quit_eval() releases heap-allocated memory at program termination
385 for (int i = 0; i < MAX_THREADS; i++)
388 delete MaterialTable[i];
390 MaterialTable[i] = NULL;
395 /// read_weights() reads evaluation weights from the corresponding UCI parameters
397 void read_weights(Color us) {
399 // King safety is asymmetrical. Our king danger level is weighted by
400 // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
401 const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
402 const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
404 Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
405 Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
406 Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
407 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
408 Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
409 Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
411 // If running in analysis mode, make sure we use symmetrical king safety. We do this
412 // by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
413 if (get_option_value_bool("UCI_AnalyseMode"))
414 Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
422 // init_attack_tables() initializes king bitboards for both sides adding
423 // pawn attacks. To be done before other evaluations.
425 template<Color Us, bool HasPopCnt>
426 void init_attack_tables(const Position& pos, EvalInfo& ei) {
428 const Color Them = (Us == WHITE ? BLACK : WHITE);
430 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
431 ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
432 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
433 b &= ei.attackedBy[Us][PAWN];
435 ei.kingAttackersCount[Us] = count_1s_max_15<HasPopCnt>(b) / 2;
439 // evaluate_outposts() evaluates bishop and knight outposts squares
441 template<PieceType Piece, Color Us>
442 void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
444 const Color Them = (Us == WHITE ? BLACK : WHITE);
446 assert (Piece == BISHOP || Piece == KNIGHT);
448 // Initial bonus based on square
449 Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
451 // Increase bonus if supported by pawn, especially if the opponent has
452 // no minor piece which can exchange the outpost piece
453 if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
455 if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
456 && (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
457 bonus += bonus + bonus / 2;
461 ei.value += Sign[Us] * make_score(bonus, bonus);
465 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
467 template<PieceType Piece, Color Us, bool HasPopCnt>
468 void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
475 const Color Them = (Us == WHITE ? BLACK : WHITE);
476 const Square* ptr = pos.piece_list_begin(Us, Piece);
478 while ((s = *ptr++) != SQ_NONE)
480 // Find attacked squares, including x-ray attacks for bishops and rooks
481 if (Piece == KNIGHT || Piece == QUEEN)
482 b = pos.attacks_from<Piece>(s);
483 else if (Piece == BISHOP)
484 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
485 else if (Piece == ROOK)
486 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
490 // Update attack info
491 ei.attackedBy[Us][Piece] |= b;
494 if (b & ei.kingZone[Us])
496 ei.kingAttackersCount[Us]++;
497 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
498 Bitboard bb = (b & ei.attackedBy[Them][KING]);
500 ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
504 mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
505 : count_1s<HasPopCnt>(b & no_mob_area));
507 ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
509 // Decrease score if we are attacked by an enemy pawn. Remaining part
510 // of threat evaluation must be done later when we have full attack info.
511 if (bit_is_set(ei.attackedBy[Them][PAWN], s))
512 ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
514 // Bishop and knight outposts squares
515 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
516 evaluate_outposts<Piece, Us>(pos, ei, s);
518 // Queen or rook on 7th rank
519 if ( (Piece == ROOK || Piece == QUEEN)
520 && relative_rank(Us, s) == RANK_7
521 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
523 ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
526 // Special extra evaluation for rooks
529 // Open and half-open files
531 if (ei.pi->file_is_half_open(Us, f))
533 if (ei.pi->file_is_half_open(Them, f))
534 ei.value += Sign[Us] * RookOpenFileBonus;
536 ei.value += Sign[Us] * RookHalfOpenFileBonus;
539 // Penalize rooks which are trapped inside a king. Penalize more if
540 // king has lost right to castle.
541 if (mob > 6 || ei.pi->file_is_half_open(Us, f))
544 ksq = pos.king_square(Us);
546 if ( square_file(ksq) >= FILE_E
547 && square_file(s) > square_file(ksq)
548 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
550 // Is there a half-open file between the king and the edge of the board?
551 if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
552 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
553 : (TrappedRookPenalty - mob * 16), 0);
555 else if ( square_file(ksq) <= FILE_D
556 && square_file(s) < square_file(ksq)
557 && (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
559 // Is there a half-open file between the king and the edge of the board?
560 if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
561 ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
562 : (TrappedRookPenalty - mob * 16), 0);
569 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
570 // and the type of attacked one.
573 void evaluate_threats(const Position& pos, EvalInfo& ei) {
575 const Color Them = (Us == WHITE ? BLACK : WHITE);
578 Score bonus = SCORE_ZERO;
580 // Enemy pieces not defended by a pawn and under our attack
581 Bitboard weakEnemies = pos.pieces_of_color(Them)
582 & ~ei.attackedBy[Them][PAWN]
583 & ei.attackedBy[Us][0];
587 // Add bonus according to type of attacked enemy pieces and to the
588 // type of attacking piece, from knights to queens. Kings are not
589 // considered because are already special handled in king evaluation.
590 for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
592 b = ei.attackedBy[Us][pt1] & weakEnemies;
594 for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
595 if (b & pos.pieces(pt2))
596 bonus += ThreatBonus[pt1][pt2];
598 ei.value += Sign[Us] * bonus;
602 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
603 // pieces of a given color.
605 template<Color Us, bool HasPopCnt>
606 void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
608 const Color Them = (Us == WHITE ? BLACK : WHITE);
610 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
611 const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
613 evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
614 evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
615 evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
616 evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
618 // Sum up all attacked squares
619 ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
620 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
621 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
625 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
627 template<Color Us, bool HasPopCnt>
628 void evaluate_king(const Position& pos, EvalInfo& ei) {
630 const Color Them = (Us == WHITE ? BLACK : WHITE);
632 Bitboard undefended, b, b1, b2, safe;
635 const Square ksq = pos.king_square(Us);
638 ei.value += Sign[Us] * ei.pi->king_shelter(pos, Us, ksq);
640 // King safety. This is quite complicated, and is almost certainly far
641 // from optimally tuned.
642 if ( pos.piece_count(Them, QUEEN) >= 1
643 && ei.kingAttackersCount[Them] >= 2
644 && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
645 && ei.kingAdjacentZoneAttacksCount[Them])
647 // Is it the attackers turn to move?
648 sente = (Them == pos.side_to_move());
650 // Find the attacked squares around the king which has no defenders
651 // apart from the king itself
652 undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
653 undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
654 | ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
655 | ei.attacked_by(Us, QUEEN));
657 // Initialize the 'attackUnits' variable, which is used later on as an
658 // index to the KingDangerTable[] array. The initial value is based on
659 // the number and types of the enemy's attacking pieces, the number of
660 // attacked and undefended squares around our king, the square of the
661 // king, and the quality of the pawn shelter.
662 attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
663 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
664 + InitKingDanger[relative_square(Us, ksq)]
665 - mg_value(ei.pi->king_shelter(pos, Us, ksq)) / 32;
667 // Analyse enemy's safe queen contact checks. First find undefended
668 // squares around the king attacked by enemy queen...
669 b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
672 // ...then remove squares not supported by another enemy piece
673 b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
674 | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
676 attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
679 // Analyse enemy's safe distance checks for sliders and knights
680 safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
682 b1 = pos.attacks_from<ROOK>(ksq) & safe;
683 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
685 // Enemy queen safe checks
686 b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
688 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
690 // Enemy rooks safe checks
691 b = b1 & ei.attacked_by(Them, ROOK);
693 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
695 // Enemy bishops safe checks
696 b = b2 & ei.attacked_by(Them, BISHOP);
698 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
700 // Enemy knights safe checks
701 b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
703 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
705 // To index KingDangerTable[] attackUnits must be in [0, 99] range
706 attackUnits = Min(99, Max(0, attackUnits));
708 // Finally, extract the king danger score from the KingDangerTable[]
709 // array and subtract the score from evaluation. Set also ei.kingDanger[]
710 // value that will be used for pruning because this value can sometimes
711 // be very big, and so capturing a single attacking piece can therefore
712 // result in a score change far bigger than the value of the captured piece.
713 ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
714 ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
719 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
722 void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
724 const Color Them = (Us == WHITE ? BLACK : WHITE);
726 Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
727 Bitboard b = ei.pi->passed_pawns(Us);
731 Square s = pop_1st_bit(&b);
733 assert(pos.pawn_is_passed(Us, s));
735 int r = int(relative_rank(Us, s) - RANK_2);
736 int tr = r * (r - 1);
738 // Base bonus based on rank
739 Value mbonus = Value(20 * tr);
740 Value ebonus = Value(10 + r * r * 10);
744 Square blockSq = s + pawn_push(Us);
746 // Adjust bonus based on kings proximity
747 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
748 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
749 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
751 // If the pawn is free to advance, increase bonus
752 if (pos.square_is_empty(blockSq))
754 squaresToQueen = squares_in_front_of(Us, s);
755 defendedSquares = squaresToQueen & ei.attacked_by(Us);
757 // If there is an enemy rook or queen attacking the pawn from behind,
758 // add all X-ray attacks by the rook or queen. Otherwise consider only
759 // the squares in the pawn's path attacked or occupied by the enemy.
760 if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
761 && (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
762 unsafeSquares = squaresToQueen;
764 unsafeSquares = squaresToQueen & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
766 // If there aren't enemy attacks or pieces along the path to queen give
767 // huge bonus. Even bigger if we protect the pawn's path.
769 ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
771 // OK, there are enemy attacks or pieces (but not pawns). Are those
772 // squares which are attacked by the enemy also attacked by us ?
773 // If yes, big bonus (but smaller than when there are no enemy attacks),
774 // if no, somewhat smaller bonus.
775 ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
777 // At last, add a small bonus when there are no *friendly* pieces
778 // in the pawn's path.
779 if (!(squaresToQueen & pos.pieces_of_color(Us)))
784 // Increase the bonus if the passed pawn is supported by a friendly pawn
785 // on the same rank and a bit smaller if it's on the previous rank.
786 supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
787 if (supportingPawns & rank_bb(s))
788 ebonus += Value(r * 20);
789 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
790 ebonus += Value(r * 12);
792 // Rook pawns are a special case: They are sometimes worse, and
793 // sometimes better than other passed pawns. It is difficult to find
794 // good rules for determining whether they are good or bad. For now,
795 // we try the following: Increase the value for rook pawns if the
796 // other side has no pieces apart from a knight, and decrease the
797 // value if the other side has a rook or queen.
798 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
800 if (pos.non_pawn_material(Them) <= KnightValueMidgame)
801 ebonus += ebonus / 4;
802 else if (pos.pieces(ROOK, QUEEN, Them))
803 ebonus -= ebonus / 4;
806 // Add the scores for this pawn to the middle game and endgame eval
807 ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
813 // evaluate_space() computes the space evaluation for a given side. The
814 // space evaluation is a simple bonus based on the number of safe squares
815 // available for minor pieces on the central four files on ranks 2--4. Safe
816 // squares one, two or three squares behind a friendly pawn are counted
817 // twice. Finally, the space bonus is scaled by a weight taken from the
818 // material hash table.
819 template<Color Us, bool HasPopCnt>
820 int evaluate_space(const Position& pos, EvalInfo& ei) {
822 const Color Them = (Us == WHITE ? BLACK : WHITE);
824 // Find the safe squares for our pieces inside the area defined by
825 // SpaceMask[us]. A square is unsafe if it is attacked by an enemy
826 // pawn, or if it is undefended and attacked by an enemy piece.
827 Bitboard safe = SpaceMask[Us]
828 & ~pos.pieces(PAWN, Us)
829 & ~ei.attacked_by(Them, PAWN)
830 & (ei.attacked_by(Us) | ~ei.attacked_by(Them));
832 // Find all squares which are at most three squares behind some friendly pawn
833 Bitboard behind = pos.pieces(PAWN, Us);
834 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
835 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
837 return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
841 // apply_weight() applies an evaluation weight to a value trying to prevent overflow
843 inline Score apply_weight(Score v, Score w) {
844 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
848 // scale_by_game_phase() interpolates between a middle game and an endgame score,
849 // based on game phase. It also scales the return value by a ScaleFactor array.
851 Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
853 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
854 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
855 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
857 Value eg = eg_value(v);
858 ScaleFactor f = sf[eg > VALUE_ZERO ? WHITE : BLACK];
859 Value ev = Value((eg * int(f)) / SCALE_FACTOR_NORMAL);
861 int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
862 return Value(result & ~(GrainSize - 1));
866 // weight_option() computes the value of an evaluation weight, by combining
867 // two UCI-configurable weights (midgame and endgame) with an internal weight.
869 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
871 // Scale option value from 100 to 256
872 int mg = get_option_value_int(mgOpt) * 256 / 100;
873 int eg = get_option_value_int(egOpt) * 256 / 100;
875 return apply_weight(make_score(mg, eg), internalWeight);
878 // init_safety() initizes the king safety evaluation, based on UCI
879 // parameters. It is called from read_weights().
883 const Value MaxSlope = Value(30);
884 const Value Peak = Value(1280);
887 // First setup the base table
888 for (int i = 0; i < 100; i++)
890 t[i] = Value(int(0.4 * i * i));
893 t[i] = Min(t[i], t[i - 1] + MaxSlope);
895 t[i] = Min(t[i], Peak);
898 // Then apply the weights and get the final KingDangerTable[] array
899 for (Color c = WHITE; c <= BLACK; c++)
900 for (int i = 0; i < 100; i++)
901 KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);